PHOTOPHYSICS OF POLYCYCLIC AROMATIC-HYDROCARBONS ADSORBED ON SILICA-GEL SURFACES .2. LIFETIME DISTRIBUTION AND SYMMETRY

In a lifetime distribution analysis of six polycyclic aromatic hydrocarbons (PAHs) adsorbed on silica gel surfaces, a dramatic photophysical effect on the surface can be seen in the PAHs where the lowest excited singlet state is of 1L(b) type. This suggests that this effect is related to the symmetry of the lowest excited singlet state of the particular molecule. In addition, a comparison of the photophysical behavior of these PAHs adsorbed on a highly dehydroxylated and on a hydroxylated silica gel surface suggests that the natures of these two types of adsorption may be different. These results show that the regularized lifetime distribution analysis is a useful tool in the surface photophysical studies.